1. Field of the Invention
The present invention relates to a simulation method of an extraction system that simulates the processing of an extraction system with extractor that mixes fluids of two phases and extracts substance included in one fluid into the other fluid.
2. Related Art
There is known, as a chemical engineering processes, solvent extraction processing which mixes fluids of two phases and extracts substance included in one fluid into the other fluid. Simulations using computers have also been utilized for analysis and evaluation of the solvent extraction processing.
In a nuclear fuel reprocessing plant, for example, an solvent extraction process is utilized for separating fission fuel such as uranium and plutonium from spent nuclear fuel. There have been proposals for simulation programs for solvent extraction process in a nuclear fuel reprocessing such as xe2x80x9cxe2x80x98Development of the Simulation Codes MIXSET and PULCO for the Solvent Extraction on the PUREX Process Reprocessingxe2x80x99, by Miyachi and Masui, PNC Technical Review, No.76, P45-51, December 1990xe2x80x9d. Simulation and analysis of the solvent extraction process in a nuclear fuel reprocessing are performed by executing such simulation programs.
Simulating various process conditions is expected to study advanced solvent extraction process for more economical, reliable, and safer reprocessing plant. Such a calculation model will be very complex and large-scale, but will require flexible and frequent modifications because of the many patterns of behavior to be studied. However, ordinary simulation programs are not easy to simulate complicated events and to change the models or mathematical equations frequently because they are designed to simulate predetermined events.
On the other hand, object-oriented software is proposed as analysis tools for design and operation of plants. For example, there is software named xe2x80x9cObject DPSxe2x80x9d being marketed by The Institute of Japanese Union of Scientists and Engineers. According to this software, programs which simulate each portion of the processes can be combined relatively easily. (See xe2x80x9cRecent trends of software technology in chemical industryxe2x80x9d, No. 486, Vol. 40, 1995 extra edition of xe2x80x9cChemical Engineeringxe2x80x9d(in Japanese), November, 1995, published by Kagaku Kogyo Sha.) However object-oriented software of this kind can not be directly applied to each concrete process. In other words, programs corresponding to each of the processes must be developed in order to be applied to concrete processes.
An object of the present invention is to provide a simulation method of solvent extraction systems which facilitates a variety of simulations including calculations of the concentration profile under conditions in which abnormal flows occur in the process. To realize this feature, on the basis of utilizing object-oriented software, a solvent extraction processing is divided into several small-scale elemental models corresponding to appropriate units, and an overall model is made up by combining these individual elements for each behavior to be studied.
Then, by such simulations, a variety of plant design or operation method can be analyzed. Therefore, plants can be designed or operated utilizing the results of the analysis. The simulation, being particularly suitable for analyzing a solvent extraction process of nuclear fuel reprocessing, can be utilized for designing or operating plants.
The present invention is a simulation method of an extraction system which simulates the operation of an extraction system with extractors that mixes fluids of two phases and extract substance included in one fluid into the other fluid, wherein the simulation method utilizes object-oriented software for dividing the operation into basic elements for calculation, and provides as basic elements composing the extractor, a mixing section for simulating separation and mixing of fluids of two phases and mass transfer between the fluids of two phases, a dividing section for simulating a divided flow of a portion of the fluids, and a merging section for simulating merging of a plurality of fluids, in order to simulate the case of a flow other than the normal flow using the dividing section and the merging section.
According to the present invention, as described above, the extraction operation is divided into basic elements of appropriate units. Application to change of models or analysis equations is therefore easy. Additionally, a variety of abnormal flows in the process other than the normal flow can be easily simulated because a portion of the fluids can be divided in the dividing section and a plurality of fluids can be merged in the merging section.
The mixing section of the present invention also performs simulation of mass balance calculation and equilibrium concentration calculation separately. Separation of mass balance calculation and equilibrium concentration calculation facilitates setting of a variety of conditions.
The present invention also provides, as basic elements composing the extraction system, a settler section for simulating flows of separated fluids in the extractor and a piping section for simulating flows of fluids in sections following the settler section. Actual operation of the extractor can be faithfully reproduced because simulation is performed along flows of fluids inside the extractor.
Further, the present invention determines the divided-flow ratio in the dividing section to simulate flows other than the normal flow insides the extractor. A variety of abnormal flows (those other than the basic flow) can be simulated by disposing a dividing section at an arbitrary location where a flow other than the basic flow occurs, and allowing the flow into a merging section to be disposed at an arbitrary location.
Still further, the extractor of the present invention is a centrifugal extractor having an overflow piping at an inflow section, as well as letting fluids of two phases flow to the outside of a rotor and mixing the two, performing centrifugation inside the rotor, and individually discharging an external fluid and an internal fluid, having been separated by a weir, wherein simulation of three states of flows other than the normal flow is performed, namely, the overflow state in which fluids flow out through the overflow piping, the entrainment occurring state in which unseparated fluids of two phases overflow the weir, and the reflux state in which a fluid that has been separated and discharged from the rotor flows back again to the section mixing the fluids of two phases. Simulation of the overflow state, the entrainment occurring state, and the reflux state in the centrifugal extractor therefore becomes possible.
Moreover, the extractor is a mixer settler extractor comprising a mixing section and a separation section using gravity, wherein simulation of three states of flows other than the normal flow is performed, namely, the overflow state in which fluids flow out through the overflow piping, the entrainment occurring state in which unseparated fluids of two phases are discharged from the separation section using gravity, and the reflux state in which a fluid that has been separated flows back again to the section mixing the fluids of two phases. Simulation of the overflow state, the entrainment occurring state, and the reflux state therefore becomes possible in the mixer settler extractor.
The extraction system of the present invention is also an extraction system for performing multistage extraction with a plurality of extractors connected. Actual extraction systems, being usually multi-staged, can be simulated by the present invention.
The present invention is also a media for storing a simulation program of an extraction system for causing a computer to simulate the operation of an extraction system with extractors which mixes fluids of two phases and extract substance included in one fluid into the other fluid, wherein the simulation method utilizes object-oriented software for dividing the operation into basic elements for calculation, and provides, as basic elements composing the extractor, a mixing section for simulating separation and mixing of fluids of two phases and mass transfer between the fluids of two phases, a dividing section for simulating a divided flow of a portion of the fluids, and a merging section for simulating merging of a plurality of fluids, in order to simulate the case of a flow other than the normal flow using the dividing section and the merging section.
In other words, the simulation method is preferably performed by using a computer, and the program is stored in hard disk or the like, and executed. Here, the program, preferably distributed via storage media such as a CD-ROM or a floppy disk, can be distributed via on-line communication.